پديد آورندگان :
محمدي، حمزه دانشگاه علوم پزشكي تهران - دانشكده بهداشت - گروه بهداشت حرفه اي، تهران، ايران , فرهنگ دهقان، سميه دانشگاه علوم پزشكي شهيد بهشتي - دانشكده بهداشت و ايمني - مركز تحقيقات ارتقاء سلامت محيط كار، تهران، ايران , عبدالهي، محمد باقر دانشكده علوم پزشكي شوشتر، شوشتر، ايران , كلانتر، مجتبي دانشكده علوم پزشكي شوشتر، شوشتر، ايران , كايداني، معصومه دانشكده علوم پزشكي شوشتر، شوشتر، ايران
چكيده لاتين :
human being. In this regard, it is necessary to provide optimal lighting in the living
environment and to show objects and enhance differential contrast, as well as preventing
visual fatigue and glare. The advancement of technology and the increased need for shift
work have made individuals, according to their type and nature of work, exposed to highintensity
light. Among such occupations, which are considered as very precise jobs, we can
mention clockwork, mapping, electronic work, etc. High levels of natural or artificial
lighting in some businesses can be considered as a harmful physical factor. In-vivo studies
have shown that exposure to light can affect fertility and the quality of semen and sperm.
Hereof, papers mostly focus on the effects of non-visible radiation or on the effect of
radiation wavelengths, and less studies have been conducted to investigate the effect of
visible light, in particular on the high intensity of lighting, on semen parameters. Since high
light level of natural or artificial sources in some workplaces may be considered as a
hazardous physical agent, the present study aimed to assess the effect of light level of 1000
lux on sperm parameters in mice.
Methods: The study population included 12 healthy male adult mice of the same age (7
weeks) with approximately the same weights (30 ± 2.5 g). Six were considered as a control
group and six were considered as case group. Animals were kept in polycarbonate Plexiglas
containers during the test and after testing time kept in special cages. Food and water were
freely access available to the animals. The average temperature of the room was 24-28°C, the
relative humidity was 60-40%, and the air velocity was 0.14-0.16 m/s. Light intensity
measured during 8 hours of daily exposure was 1000 lux and at animal room less than 100
lux were measured by a lux meter. The amount of light needed for testing was only provided
through a projector equipped with 400-watt metallic halide bulbs with white light.
Experiments were conducted under controlled conditions for a period of five consecutive
days and eight hours of exposure daily. At the end of the exposure scenario, animals of each
group were anesthetized with Ketamine-xylazine injections, the epidermis of the testicles
was stretching out and put on in a culture medium for semen analysis. Paraffin molds and 5-
micron slices were provided and all tests related to tissue index were performed on the
samples. Also, by optical microscope with magnification of 400x, spermatogonium,
spermatocyte, spermatid and sperm cells was counted. The internal and external diameter of
the sperm tubes was calculated using the Image J software. The mean three-time intra-group
replication of the data with a significant level of 0.05 was reported. Data were analyzed by
one-way ANOVA and Tukey's post hoc tests.
Results: in assessing the morphology of sperm in case group, the more abnormalities (with
hairpin curved sperm) was found than the one of the control.
There was a significant difference of the internal diameter of the spermatozoa tubes (case:
97.11 ± 1.79 μm; control: 66.82 ± 1.02 μm) between the case and control groups (P<0.01),
while there was no significant difference between the two groups in case of the external
diameter (case: 160.27 ± 1.95 μm; control: 161.98 ± 1.33 μm) (P>0.05). The percentage of
total motile sperms (case: 60.7 ± 0.96; control: 72.4 ± 1.02), percentage of sperm with
normal morphology (case: 45.50 ± 3.58; control: 73.35 ± 1.6) and the percentage of living
sperm (case: 58.68 ± 1.44; control: 74.36 ± 1.65) were significantly different between the two groups (P<0.01). No significant difference in the number of sperm in millions (case:
4.11 ± 1.11; control: 4.51 ± 0.09) was observed between the two groups (P> 0.05).
Microscopic images showed that the internal diameter of the spermatozoa tubes in the case
group have been changed in comparison with the control group. Result show tissue
degradation, disruption of spermatogenic cell and destruction of the medial part of the
spermatozoa tubes in the case group as compared to the control group. The presence of
irregularity, entanglement and abnormalities in the case group was clear compared to the
control group.
Conclusion: The aim of this study was to investigate the effect of exposure to light 1000 lux
on sperm parameters in male mice. Previously, a similar study on the effect of high intensity
lighting on reproductive ability and quality of semen was not reported. While today,
exposure to high-intensity light in precise jobs and shift works is so common. According to
the findings of this study, exposures to light 1000 lux reduced motility, percentage of natural
morphology and rate of living sperm, which is expected to increase the possibility of
different degrees of infertility in male. Also there was an increase in the internal diameter of
the spermatozoa tubes due to exposure with 1000 lux, indicating cell differentiation and
death in a large number of reproductive and germ cells of different classes. Cellular
mechanisms regarding the interaction between visible light and sperm are still debatable.
Most researchers believe that the first step in finding the interaction between light-cells is the
formation of reactive oxygen species (ROS) by light-sensitive elements in endogenous cell.
Although in male reproduction, ROS is known to be harmful to sperm function, it has now
been shown that very low concentrations of ROS in signal transmission pathways lead to
sperm acrosome responses, which seems essential for fertilization. The results of other
studies show that visible light can change the redox state of sperm cells by inducing ROS
production. Since one of the most important functions of the regulator cells is to maintain
cell redox homeostasis, this change can modulate the intracellular movement of Ca2+.
Changes in ROS and Ca2+ both play a vital role in controlling sperm motility and
fertilization capacity of mammalian sperm. In addition, a study has shown that visible light
increases the amount of ATP (Adenosine triphosphate) in sperm cells. However, more
studies are needed to fully investigate the effects different intensities of visible light
exposure on the sperm fertilizing ability. Since the precise determination of the cellular
redox state depends on the cellular conditions and the parameters of the light used for
radiation, the optimal light conditions for each animal's spermatozoa for therapeutic purposes
should be determined. Considering that studies focus mainly on lower intensity of visible
light, in order to conclude definitively, more comprehensive studies are required on different
animal species or on human sperms. Due to the fact that today, in precise and high-precise
jobs, exposures of people with high-intensity radiation occur, it is advisable to take
appropriate control measures in the workplace in order to prevent the potential adverse
effects of exposure to high intensity illumination. In conclusion, according to our findings,
exposure to the light level of 1000 lux may reduce total motility, natural morphology
percentage and survival rate of sperms, which is expected to increase with the possibility of
different degrees of infertility with male factor over time. There was also an increase in the
internal diameter of the sperm membranes due to the exposure to 1000 lux, indicating cell
differentiation and death in a large number of different germ cells.
